On 2005-10-26, Tom Lane <[EMAIL PROTECTED]> wrote: > Andrew - Supernews <[EMAIL PROTECTED]> writes: >> Um, what? Under what conditions is it permissable for simple arithmetic on >> (only) timestamptz values (which may have originated in different timezones >> neither of which is the current one) to be dependent on the current timezone >> setting? > > Timestamp subtraction will give different answers depending on whether > there's a DST adjustment in between.
no, it _WILL NOT_. In your example, the result is different between timezones because the _input data_ is different. '2005-10-31'::timestamptz designates a different time in US/Eastern than it does in Japan, or UTC, or whatever. Or to put it in terms of the code: in 8.0, timestamptz_in is stable rather than immutable (since it depends on timezone), while timestamptz_mi is immutable (result depends only on the input values). In 8.0, I'm guaranteed that for timestamptz values, a+(b-a) = b in all cases regardless of timezone. 8.1 has broken that. > BTW, if we were doing subtraction symbolically as I think we should, > these *would* give the same answer, ie, '3 days' in both cases. Care to > rethink your opposition to that idea? No. If you want symbolic subtraction, that's what age() is for. If you break the subtraction operator, you leave no means of doing _accurate_ subtraction. -- Andrew, Supernews http://www.supernews.com - individual and corporate NNTP services ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org
